1. Field of the Invention
The present invention relates to an apparatus for locating and positioning a medical device in a patient. More particularly, the present invention relates to a medical device for delivering therapeutic substances, which is steerable through body lumen or cavities and positionable within organs or tissue from a position external to the body.
2. Related Art
The number and variety of medical devices available to repair the effects of cardiovascular disease has increased rapidly over the last several years. More particularly, alternatives to open heart surgery and cardiovascular by-pass surgery have been extensively investigated, resulting in the development of non-surgical procedures. These procedures are typically directed toward the reduction of stenosis within the vasculature of a patient or the generation of new blood vessels in the body for restoring blood flow to tissues after injury or trauma.
Some medical devices, such as those developed to control the effects and occurrence of angiogenesis, such as Percutaneous TransMyocardial Revascularization (PTMR) and gene therapy, may use a catheter for delivering therapeutic substances to diseased vessels and ischemic myocardium. Angiogenesis is a naturally occurring process, both in health and in disease states, where new blood vessels are grown in the body for healing wounds and for restoring blood flow to tissues after injury or trauma. For example, in females, angiogenesis occurs during the monthly reproductive cycle to rebuild the uterus lining and to mature the egg during ovulation. Angiogenesis also occurs in various disease states, such as cancer, diabetic blindness, age-related macular degeneration, rheumatoid arthritis, coronary artery disease, stroke, and other disorders.
Although angiogenesis occurs naturally in the body, various procedures have been developed to artificially control the occurrence and effects of angiogenesis. For example in a PTMR procedure, a laser is used to create small channels in the diseased tissue. The channels re-establish direct blood flow to the tissue and allow oxygen-rich blood to saturate the oxygen-starved tissue.
Another procedure used to promote angiogenesis involves gene therapy. For this procedure, genetic material is delivered directly to the diseased area of the body. In particular, genetic material, such as Vascular Endothelial Growth Factor (VEGF), is incorporated into gene delivery vehicles called vectors, which encapsulate therapeutic genes for delivery to the diseased cells. Many of the vectors currently in use are based on attenuated or modified versions of viruses. The vectors may also be synthetic versions in which complexes of DNA, proteins, or lipids are formed into particles capable of efficiently transferring genetic material.
Medical devices used for non-surgical procedures, such as PTMR and gene therapy, generally include elongate tube-like members (e.g., catheters), which may be inserted into the body, either percutaneously or via a body orifice. Such medical applications frequently require the use of catheters having the ability to negotiate a variety of tortuous body lumens and body cavities. Many attempts have been made to provide catheters that are steerable to enable the catheter to be aimed at specifically targeted tissue or advanced through tortuous body lumens and/or body cavities. For example, in one type of balloon catheter a deflection wire is provided which extends along the entire length of the catheter. One drawback associated with this type of balloon catheter is that the deflection wire can be axially displaced to cause deflection of the catheter tip in only one direction. Thus, to be guided, the entire catheter must be rotated or torqued. Moreover, the design can require a relatively large diameter deflection wire, which can substantially increase the diameter of the catheter so as to preclude the use of the catheter in small lumen coronary applications. Limited catheter tip steerability results in greater time spent in the body and significantly elevated risk of trauma both to the vascular intima and to the patient in general.
The present invention provides a medical apparatus and method of use for delivering a therapeutic substance to a target location in the human vasculature, for example, to control the effects and occurrence of angiogenesis. The present invention provides a catheter assembly that can be steered through the vasculature in more than one direction, without the need for rotating or torqueing the catheter assembly. Increased steerability can result in less time spent in the body and significantly reduce the risk of trauma both to the vascular intima and to the patient in general.
The invention provides a catheter assembly, which can be used for delivering the therapeutic substance to diseased vessels and ischemic myocardium. The catheter assembly can include a translating body assembly and a fixed body assembly mated together in a telescopic configuration to allow the translating body assembly to move relative to the fixed body assembly and facilitate the delivery of the therapeutic substance to a targeted area. The translating body assembly includes an inner member, which can be modified to provide flexibility, pushability (i.e., column strength) and torqueability to the inner member. The modification can be made substantially on the distal section of the inner member to allow the inner member to be steered to contact diseased tissue and to navigate through tortuous coronary lumen. The modified distal section provides enough flexibility to facilitate the steering of the distal tip, while maintaining enough column strength to provide adequate pushability and torqueability. A hollow needle can be coupled to the distal end of the modified inner member to penetrate through tissue and enable delivery of therapeutic substances to the tissue.
To provide steerability to the modified inner member, the translating body assembly can also include a steering device, which can include two tendons coupled along the sides and fixed distally to the inner member proximal to the hollow needle. The design of the catheter assembly maintains a relatively small diameter, since the dual-tendon arrangement minimizes the need for a large diameter deflection wire. Each tendon is coupled to a puller at the proximal section of the catheter assembly. Movement of the puller causes each tendon to move the distal section of the inner member. Beneficially, the catheter assembly can be displaced in at least two directions to cause deflection of the catheter assembly.
In one aspect of the invention, a guiding catheter including an anchoring device is provided in accordance with the present invention. The guiding catheter can be a hollow sheath having an inner lumen that extends the length of the sheath. The inner lumen is sized to slidably receive various intraventricular devices, such as the catheter assembly. The anchoring device is disposed at the distal end of the guiding catheter to aid in guiding the catheter assembly to the treatment area and for holding the catheter assembly in position to facilitate the extension of the hollow needle into the target tissue. Once in the treatment area, the anchoring device can be actuated and secured using friction and compressive forces. The distal end of the catheter assembly can be delivered through the lumen, such that the needle can be oriented at the designated treatment area using the pullers. The operator holds the handhold and urges the translating body assembly forward, which causes the hollow needle to move out from the distal end of the outer member and engage the tissue. Once the needle is engaged with the tissue, therapeutic substances can be delivered to the tissue.